Cross-sectional study of youth physical activity (PA) and sedentary activity (SA) patterns has revealed determinants of and disparities in accrual based on 5 or 6 factors and dozens of variables. By identifying variables that influence PA/SA accrual, more effective interventions can be designed to reverse the trend in PA decrement observed in many populations. Absent from this research is how religion, specifically religiosity, may play a role in the accrual of PA/SA. Judaism in particular has been understudied even though Jewish doctrine directly affects adherents’ daily activities. This study aimed to measure (a) differences in accrual of weekend SA/PA by religious affiliation, and (b) the association between religiosity and accrual of PA/SA. The Self-Administered Physical Activity Checklist (SAPAC) was completed by 437 students (response rate = 57.5%; female, 54.9%; M age = 12.8 ± 0.88) attending Jewish day schools in two large Western cities in the USA. Nine measures of religiosity (e.g., degree of Sabbath observance, synagogue attendance during previous week, comparative religious commitment) were based on recommendations in the literature including epidemiological research conducted on Israeli Jews. Orthodox children accrued less Saturday PA (kcal•kg-1) [t (338) = 2.97, p < .01 (one-tailed), d = .33] and less Saturday SA (hr) [t (333) = 5.54, p < .001 (one-tailed), d = .63] than Non-Orthodox children. No differences for PA or SA accrual were noted for Sunday. Religiosity measures were entered into an oblique rotation factor analysis, yielding three distinct factors, each composed of items ≥ .40-criterion for factor loading. The factors were labeled Observance (α = .72, 4 items), Devotion (α = .53, 2 items), and Doctrinal Consonance (α = .48, 3 items). Factor scores were correlated with weekend accrual of PA/SA. Pearson correlations of practical significance (i.e., p < .05; r = 0 Ï 95% CI; |r| > .2) included: Observance-Saturday PA (r = -.21), Observance-Saturday SA (r = -.37), and Doctrinal Consonance-Saturday SA (r = -.21). Most items that loaded on Observance were behavioral and are either mediated or under direct control of parents (socio-cultural determinant of PA). Parents also influence variables found on the Doctrinal Consonance factor over the course of rearing children. In summary, while religious regulations restrict engagement in PA and SA for Orthodox Jewish children on Saturday (Sabbath), religion as a determinant of PA/SA in young adolescents may be a subset of parental influence.Keyword(s): multiculturalism/cultural diversity, physical activity, wellness/disease prevention